Tim Furniss/LONDON

The crew of the Space Shuttle Atlantis STS101 are scheduled to land back at the Kennedy Space Centre, Florida on 29 May after the International Space Station (ISS) mission 2A.2A.

The Atlantis crew erected more equipment onto the exterior of the linked Unity-Zarya modules of the fledgling space station and conducted repairs and maintenance inside, including the replacement of four batteries in Zarya. They also stocked the station with over 1,500kg (3,300lb) of equipment, including fans, fire extinguishers and clothes, for the first Expedition Crew, to be launched in October.

The first of a series of firings of the Shuttle's reaction control thrusters was made on 23 May, to raise the orbit of the ISS eventually to a 376km (230 miles) apogee after the orbit dipped to a low of 333km. It had been losing 2.4km a week.

The STS101 crew used an improved ducting system to keep air circulating inside the modules to prevent the build up of impurities, including carbon dioxide, which affected the last crew of STS 96 in May last year, causing nausea, fatigue and sickness.

Almost a year since the last crew reached the fledgling 35,000kg, 24m (80ft)-long ISS Unity-Zarya module combination, two of the STS101 crew completed a 6h 44min spacewalk fixing a 1.3m, 95kg long crane to the side of the station after it was left hanging loose during a previous spacewalk.

Further tasks included fixing parts to a larger Russian Strela crane which will eventually be 15m long, and replacing a failed communications antenna. The Atlantis had docked with the ISS on 21 May, following the launch from the Kennedy Space Center on 19 May.

The STS101 mission should be followed on 12 July by the much-awaited launch of the Russian Zvezda service module. The Proton launch of Zvezda will be preceded by two Proton launches carrying communications satellites. Problems with these launches would delay further the Zvezda.

Successful berthing of the Russian module in July will turn the spotlight on NASA and Shuttle missions over the next few months. NASA has been able to hide its problems behind Russian delays with Zvezda but with the US Laboratory Module, Destiny, experiencing completion problems its anticipated January launch is problematical.

Source: Flight International